Wide angle photographic lens

ABSTRACT

A wide angle photographic lens or objective, having a rear member (behind the central vertex distance or space) and a front member, the front member being composed of three or more groups or assemblies. Five specific examples are disclosed, falling into three general configurations. Various limits are stated for the relationship of the various lens elements or groups of elements to each other, and if these limits are followed in designing the lens, an objective of excellent quality and wide angular field of view can be obtained.

United Sta 4 7+0 Glatzel [54] WIDE ANGLE PHOTOGRAPHIC LENS [75] lnventor: Erhard GlatzeLHeidenheim,

Germany [73] Assignee: Carl Zeiss Stiftung (a.k.a. Carl Ziess), Heidenheim on the Brenz, Wurt temberg, Germany 221 Filed; Sept. 19,1973

21 Appl. No.: 398,774

[30] Foreign Application Priority Data Sept. 21, 1972 Switzerland 13917172 [52] U.S. Cl. 350/214, 350/176 [5| Int. Cl. G02b 9/00, G02!) H00 [58] Field of Search 350/214, 176

[56] References Cited UNITED STATES PATENTS 12/1970 Mori 350/214 X Feb. 4, 1975 3,622,227 1 1/197] Shimizu .L 350/214 3,663,095 5/l972 Mori 3,736,049 5/l973 Shimizu 350/2 l4 Primary Examiner-Paul A. Sacher Attorney, Agent, or Firm-Stonebraker & Shepard [57] ABSTRACT A wide angle photographic lens or objective, having a rear member (behind the central vertex distance or space) and a from member, the front member being composed of three or more groups or assemblies. Five specific examples are disclosed, falling into three general configurations. Various limits are stated for the relationship of the various lens elements or groups of elements to each other, and if these limits are followed in designing the lens, an objective of excellent quality and wide angular field of view can be obtained.

* 13 Claims, 3 Drawing Figures PATENTEU FEB 4|975 SPEET 3 RF 3 1 WIDE ANGLE PHOTOGRAPHIC LENS BACKGROUND OF THE INVENTION Many photographic objectives or lenses of the wide angle" type are known in the art. The object of the present invention is to provide a wide angle lens of improved design, having a relative aperture within the range of about 173.8 to f/2.8 or more, characterized by a useful field of view with an extremely high picture performance, whose angular diametrical field of view is greater than 85 and can extend up to about 1 or even more.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a lens diagram illustrating a lens according to Examples 1 and 2 of the following tables;

FIG. 2 is a similar lens diagram illustrating a lens in accordance with Example 3 of the following tables; and

FIG. 3 is a similar lens diagram illustrating a lens in accordance with Examples 4 and 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As already mentioned, the invention relates to a very wide angle lens giving very high picture performance through an angle of view (diametrical angle) which is greater than 85 and can extend up to about 110 or more. The lens, has what may be described as a rear member, behind the diaphragm space or central aperture space indicated in the drawings at CS, and what may be described as a front member forwardly of such diaphragm space or central vertex space.

In all of the views of the drawings, the rear member is indicated in general by the reference characters Hgl, being an abbreviation for the German word Hinterglied," and the front member is indicated in general by the reference characters Vgl, an abbreviation for the German word Vorderglied.

The rear member consists of at least three members or components in air. The construction of the rear member corresponds in general to constructions which have been proposed for the rear members of wide angle lenses in, for example, German Pat. Nos. 1,187,393, and 1,220,164, and 1,250,151, and 1,250,152, and

1,250,153, and others, and in which both the negative space CS, as group (a), group (b), etc. The form of lens illustrated in FIG. I has only three groups forwardly of the aperture space, and they are respectively indicated in general in FIG. 1 by the reference characters Gr. (a), Gr. (b), and (c). In the construction shown in FIG. 2, there are four groups in the front member, the first three (in a direction forwardly from the aperture space) being indicated in general by thesame reference characters just mentioned, and the fourth or front group being indicated in general by the designation Gr. (d). In the construction shown in FIG. 3, there is also a fourth group designated as Gr. (d), but in this instance the group (d) is formed by only a single lens element rather than a plurality ofelements, and so is to be regarded as the equivalent of a group, and is so designated. However, in the following parts of the specification and the claims. the word "group" is intended to be interpreted broadly enough to cover a single lens element constituting the equivalent of a group of two or more elements.

According to the invention, the above mentioned front member of the lens is constructed in such manner that in each of the individual groups constituting the front member, the group has a negative part or component, preferably of meniscus shape, inserted in front of a positive part or component, in such manner that these two parts enclosed between them a diverging-acting air space or negative air lens, whose more strongly diverging glass-air surface is concave toward the shorter conjugate of the lens system, i.e., toward the image. These air lenses are designated in sequence, from the central vertex space or diaphragm space forwardly, by the characters a and B and y, in the case of lenses having three groups in the front member, with the further designation of 8 if the lens has four groups in the front member.

Furthermore, according to the invention, the individual parts or components of the front member of the I lens are so dimensioned and constructed that they comply with or fulfill simultaneously all of the conditions. set forth in the following paragraphs respectively numbered (1) through (4), and also the further condition specified in numbered paragraphs (5) and (6) if the lenses are to be of the character to which those paragraphs apply. v

l. The paraxial individual focal length (f,,) of the rearmost group Gr. (a) of the front member is between the limits of 0.75 times and 2.25 times the equivalent focal length (F) of the entire lens system.

2. The absolute value ofthe paraxial focal length (1],) of the preceding group part Gr. (b) next preceding Gr. (a) is between the limits of 9.0 F and 2.2 F.

3. The numerical value of the paraxial focal length (f of the combination of the two groups Gr. (c) and Gr. (b) together has an absolute value between the limits of 2.25 F and 5.65 F.

4. In case the lens system has a fourth group in the front member, instead of merely three groups, then the paraxial focal length (f,) of this fourth group Gr.(d) located in front of the group Gr. (c) is, in its negative value, within the limits of 5.5 F and 8.5 F.

5. In case the lens is to have a useful angle of view, with full aperture, which exceeds approximately then the air lens refractive power ((1), as the surface refractive power sum of the two radii of curvature which close the air lens y in the group Gr. (c) is so dimensioned that the negative value of da is within the limits of 0.25 I and 0.45 I in which D is the equivalent refractive power of the entire lens system, this being l/F. In this way the result is obtained that in this group with a large beam cross section prevailing therein, if the upper limit just mentioned is not exceeded, the zone intermediate errors of the wide opened and/or inclined ray beam can not only be definitely avoided but can be kept very unexpectedly small.

6. In case the front member is constructed with a total of four groups rather than merely three, then according to the invention a particularly advantageous picture performance is obtained if the parts are so dimensioned and constructed that the air lens refractive power (4, of the air lens 8 of the front group Gr. (d) is, in its negative value, within the limits of 0.] 1 and of the lens as numbered consecutively from left to right, and the radius of curvature of the front face (left face) of each lens element is indicated by the letter R with a subscript corresponding to the consecutive num- ().4 I in which I) is the equivalent refractive power of her of the particular lens element. while the radius of the complete lens system, or l/F. the rear face (right hand face) ofthe each lens element The construction of the rear member of the lens has is indicated by R with a subscript corresponding to the already been mentioned above. consecutive number of the element. In the tables. plus it is another feature of the invention tha in the vicinsigns with respect to radii indicate surfaces which are ity of the central vertex space or diaphragm space 10 convex toward the incident light. and minus signs indi- (CS), one of the lenses is split up by a finite inner air cate surfaces concave toward the incident light (that is. spacing, to provide a space in which a filter can b convex toward the rear). The tables also show the axial lectively inserted or removed as d sired Wh a filt thicknesses of the individual lens elements, indicated is used in such a space, it can be a filter of particularly y T With a b crip corresponding to the consecutive small diameter, without the mount of the filter causing number of the individual lens element, and the axial injurious vegnetting for the strongly inclined lateral p i g between lens elements indicated by 5 h a beam. Preferably the lens which is split in this way to Subscript Corresponding to the number of the Space as p vide a pa for th filt i th l f i th numbered consecutively from front to rear. Zero spacpositive part of the first group Gr. (a) directly in front ing indicates lens elements cemented to each other. All of the aperture or diaphragm space CS, This is iil spacings greater than zero refer to air spacings. t at d b th i FIG, 2 a d i FIG, 3, I F|(] 2, th filt Also, in the tables, the index of refraction ofthe glass is sh w i a Space b tw l l t L d L used for each lens element is given in the column which two elements together can be considered as the headed N, and this refers to the yellow d-hhe 0f the positive part of the group Gr. (a). In FIG. 3, the filter hum ePeetrum whose wavelength if 5376 Angstrom i shown i a space b t th l elements L d units. The refractive index based on this line is shown L,,, which two elements together can be considered as in Commercial Catalogues of manufacturers of constituting the positive part of the group Gr. (a). optical glasses. The Abbe number or index of disper- In those lenses of the present invention where the 0f the glass d for each tens element is give" in angle of view is greater than l00, it has proven particuthe tahte ht h eohlmh headed l l l advantageous to b i h f m group GR ,1 as All l1near dimensions are given w1th reference to the close as possible to the next group Gr. (0) behind it, so eqthtateht focal length whleh regarded t that that the front opening of the lens, and thus its front diis, F: 1-0000 The vafloue tables h t with ameter, within the scope ofa pre-established avoidance SPeet to each example, the lhtehttedfetattve aperture of vignetting, makes it possible to obtain the smallest and the useful total angle Ofvlew lhdleatett y 0 and possible dimensioning. This is accomplished, according the hack focus or back focal g h )"f y to the invention, by the fact that the positive refractive with reference to a remote Object at lhhhtty- The rather power of the converging component behind the front g image-eldetoeusor back focus of the new tenses air lens 8 in the front group Gr. (d) is distributed over of the Present lhvehttoh PttwtdeS a large tree axtat the lens surfaces of the front lens. As a result ofthis, the p e g between the test slhtltee ofthe lens y m and positive partial lens itself can be dispensed with. In this 40 the ge P thus h l g these new tenses Suitable way the negative-acting front meniscus, as illustrated at eh use with P mirror reflex Camera, where L, i FIG 3 becomes h equivalent f h f om group f1c1ent space 15 needed between the rear surface of the components L, and L illustrated in FIG. 2, and the e y m and thehhage plane for Operation of the front meniscus L, can be positioned directly against the pivoted mtrrotwlde g e lenses of t) shortteeat front negative meniscus L2 of the next group G[ (C)7 so length has often been dlfflCUit [9 provlde SllfflCleIli. that there is a minimum spacing, as illustrated in FIG. Space for a pivoted mirror, t thls dtfheutty 15 Over- 3 come by the lens construction according to the present invention. v In the accompanying drawings, the lenses in accor- Table l and Table 2 gives specific data for Example dance with the present invention are illustrated dia- I and Example 2, which are lenses or objectives acgrammatically or schematically, using reference charcording to the general configuration illustrated in FIG. acters which have been referred to above in this text, I of the drawings, Table 3 gives specific data for Examor which will be mentioned below or will be readily unpie 3, an objective of the general configuration illusderstood by those skilled in this art. As usual in conventrated in FIG. 2 of the'drawings. Table v4 and Table 5 tional lens diagrams, the light is assumed to travel from give specific data for Examples 4 and 5, constituting left to right, the individual lens elements are designated lens systems or objectives of the general configuration by the letter L with a subscript indicating the number illustrated in FIG. 3 of the drawings.

Table I (Example I) 1.000 rm: 2w, 88 5" 1.923 F Lens Rutlii 'l'hickncsses N V and spacings R, +2249 L, T, 0.105 1.091 54.7

Table 4 -Conlinued (Example 4) F L000 173.5 2w,= 110 s 2.334 F Lens Radii Thicknesses N V and Spacing:

S. 0.007 R. +l .349 L1 T, 0.047 1.788 47.4

S. 0.231 R. +1 .760 L. T. 0.383 1.785 26.1

S. 0.056 plane T. 0.052 filter 1.522 59.5 plane I S. 0.03 R. -l6.74 L. T.. 0.176- 1.465 65.7

S CS 0.1 15 R]. -1

' T 0.469 1.785 26.1 Ry +2.46) n 0 T.. 0.001 1.510 59.0 R' +2.70l

S 0.068 R" -3.487 L T 0.142 1.465 65.7

R' -0.8'70 8.. R" -4.205 L I '1' 0.165 1.465 65.7

Lem L is the equivalent of the group Ghll). The negative componeml in developed as a double! end innming compotile mrlace: are dlilflll u R. and R'..

Table 5 (Example 5) F= 1.000 173.5 2w,= 110 s'=2.357 F Lens Radii Thicknesses N V and Spacings S'. 0.932 R. +4.039 L. T, 0.139 1.691 54.7

S. 0.656 R. +l0.l 5 Y L. T. 0.342 1.785 26.1

S 0.008 R. +2.859 L. T. =0.l68 L713 53.9 R. +1.277

S. 0.457 R. +2.423 L. '1. 0.915 1.713 53.9'

S. 0 R. l.324" L. T. 0.223 1.564 43.8

S. 0.004 R. +1.740 L, T. 0.048 1.788 47.4

' S. I 0.223 R. +1 .7 l 5 v L. 'l. 0.368 L785 26.1

S. 0.049 plane- '1. 0.053 filter 1.522 I 59.5 plane Table 5-Continued (Example 5) F= 1.000 fl3.5 2w,= 110 s'=2.357 F Lens Radii Thicknesses N V and Spacings Lg T 0.177 1.465 65.7

S CS 0.106 R -l.55l L T 0.510 1.785 26.1

' V S 0.079 R -2.604 L T 0.165 1.465 65.7

S 0.004 R +1334 L T 0.182 1.465 65.7

Lens L. is the equivalent of group Gr. (d).

In the customary scientific nomenclature, the refrac- In each case we fundamentally have 1 2R. In Extive power of an individual lens surface is defined asq) (n' n) R and thus the sum of several successive area refractive powers can be written as 05 9+ as has been done in the preceding description for the air-lens refractive powers.

Furthermore, the corresponding numerical values for the five examples given in foregoing Tables 1 through 5 are set forth below in Table 6, for each individual feature. It is pointed out by 'way of explanation that in Example 4 (Table 4) thenegative lens which is located in the first position in the rear member and faces the aperture space is developed as two lenses, whereby the particularly advantageous possibility is obtained of making the second one of these two lenses from a material of very low refractive power. The composite surface between the first and second partial lenses which together make up the negative lens L are designated respectively as Ry and R' Table 6 ample 2, the c-values in detail are:

c. 2.493060 X10- in Example 4. these values are:

The ranges stated in the claims are based on the highest and lowest values given in foregoing Table 6 for each feature, plus or minus a tolerance of 5 per cent, that is 5 percent added to the highest value and 5 percent subtracted from the lowest value for each feature in Table 6. These values originally given in Table 6 and the adjusted tolerance values are given for convenience in the following table.

Feature Example 1 3 4 5 1. 1.194 F 1.345 F 1.957 F 1.680 F 1.929 F f, 5.659 F 7.760 F 2.561 F 3.670 F 3.196 F f.,, 4.960 F 5.117 F 2.529 F 3.551 F 2.890 F r,,- 7.356 F 6.245 F 6.135 F 69 0.312 1 0.3 2 b 0.311 0.371 o 0.306 1 -5 0.32042 0.1530 0.1790

Two of the five examples given in Tables 1 through Table 7 5 are provided with an aspherical surface. In Example 2 (Table 2) the rear surface R of the negative lens L r al Highest +5 1 Lowest -57, in the rear member is developed as a deformed surface, I and the value of R,. indicated in Table 2 is the vertex r L957 F 2055 F H94 F 7 34 F rad1us of thls surface at the locat1on of the optical ax1s. r 7.761) F 11.14:; F 2.561 F 2.435 F In Example 4 (Table 4) the rear outer surface R' of "f; the negative doublet L is also a deformed surface. and 0.371 0 0.390115 0.306 1 0.291 t: in this case also the numerical value of R' indicated 0453 0145 in Table 4 is the value of the vertex radius of this surface at the location of the optical axis.

These deformed surfaces are generally determined by the shaft height (Pfeilh'dhen) equation erture space and a front member in front of said aperture space, said rear member comprising at least three lens elements each with air on both sides, the forward element adjacent said aperture space being a negative element followed in a rearward direction by two positive elements, said front member comprising at least three groups oflens elements, each group having a negative component at the front ofthe group and a positive component rearwardly of such negative component, the negative component and positive component of each group enclosing between them a diverging-acting air space constituting a negative air lens. each of said air lenses having a more strongly diverging glass-air surface which is concave toward an image at the rear of the lens system, the successive groups in order from the aperture space forwardly being respectively designed Gr. (a) and Gr. (b) and Gr. (0), the lens elements being so constructed that:

1. The paraxial focal length (fa) of the rearmost group Gr. (a) of the front member is between the limits of 1.134 times and 2.055 times the equivalent focal length (F) of the entire lens system.

2. The absolute value ofthe paraxial focal length (f,,) of the group Gr. (12) is between the limits of 8.148F and 2.433 F.

3. The numerical value of the paraxial focal length (f, of the combination of the two groups Gr. (0) and Gr. (/1) has an absolute value between the limits of 2.40 I" and 5.373 F.

2. A lens system as defined in claim 1, having in its front member a fourth group Gr. (d) arranged forwardly of Gr. (c), the paraxial focal length (f,,) of this group Gr. (d) is, in its negative value, within the limits of 5.826 F and 7.724 F.

3. A lens system as defined in claim 2, wherein said 35 fourth group Gr. (d) consists of only a single lens element which element is negative and which acts as the equivalent ofa group havingboth a negative and a positive element, the air lens of said fourth group Gr. (d) being formed between the rear surface of said single element and the front surface ofthe negative component at the front ofthe next succeeding group Gr. (c) behind said fourth groupGr. (d).

4. A lens system as defined in claim 2. wherein the air lens refractive power (d) of the air lens (6) of the fourth group Gr. (d) is. in its negative value, within the limits ofO. 145 I and 0.336 1 in which I is the equivalent refractive power of the entire lens system. being l/F.

5. A lens system as defined in claim 4, characterized by the fact that said fourth group Gr. (d) does not include any positive lens element. and that the air lens (8) of the fourth group is formed between a meniscus shaped negative lens of the fourth group and the front lens of the third group Gr. (0).

6. A lens system as defined in claim 1, wherein the air lens refractive power (dz, as the sum of the surface refractive powers of the two radii of curvature enclosing the air lens in the group Gr. (0) is so dimensioned that the negative value of 4w is within the limits of 0.291 I and 0.390 1 in which I is the equivalent refractive power of the entire lens system, being HP.

7. A lens sytem as defined in claim 1, characterized by he fact that a lens component in the vicinity of'said aperture space is divided into two lens elements with a finite air space between them, and a filter is interposed in said air space.

8. A lens system as defined in claim 7. wherein said divided component is the component next in front of said aperture space, being the rearmost component of the rearmost group Gr. (0) of the front member (Vgl of the lens system.

9. A lens system as defined in claim 1, wherein the characteristics of the lens elements and their spatial relationship to each other are substantially in the proportions indicated by the data in the following table:

Lens Radii Thicknesses N V and Spacings R, +2.249 L T, 0.105 1.691 54.7

R, +1127 R, +2382 L, T, 0.263 1.717 29.5

S, 0.005 R, +1536 I L, 1 0.060 1.713 53.8

5, 0.362 R, 5.772 L, l', 0.574 1.669 45.0

S, 0 R, 0.864 L, T, 0.126 1.805 25.4

S, 0.007 R, =+1.409 L, T, 0.059 1.713 53.8

S, 0.077 R, +0.743 L, T, 0.589 1.622 36.00

R, 0.7l6 S, C8 0.148

R, 0.815 L, T, 0.144 1.805 25.4

S, 0.059 R, l .482 L 7 T, 0.134 1.504 67.0

S, 0.003 R,, 3.803 L T,, 0.107 1.603 60.5

15 wherein all linear dimensions of radii, thicknesses. and spacings are expressed in proportion to the equivalent focal length of the entire lens sytem. which is consid ered as unity, and the reference letters and numerals have the respective meanings explained in the foreg0- ing specification.

10. A lens system as defined in claim 1, wherein the characteristics of the lens elements and their spatial relationship to each other are substantially in the proportions indicated by the data in the following table:

wherein all linear dimensions of radii. thicknesses. and spacings are expressed in proportion to the euqivalent focal length of the entire lens system. which is considered as unity. and the reference letters and numerals have the respective meanings explained in the foregoing specification.

11. A lens system as defined in claim 1. wherein the characteristics of the lens elements and their spatial relationship to each other are substantially in the pr0p0rtions indicated by the data in the following table:

Lens Radii Thicknesses N V and Spacings R, +2.7549 l., T, =0.l224 1.6910 54.71

S, 0.5516 R, +3.5320 L, T, 0.2765 1.8052 25.43

s, 0.0030 R, +2.4020 L, T, 0.0744 1.7130 53.85

S, 0.4677 R, 5.0772 L, T 0.8062 1.7130 53.85

S, 0 R 0.8937 L, T, 0.0656 1.5731 42.58

' S, 0.1064 R, +1.0377 1. T 0.0546 1.6910 54.71

S, 0.2085 R, +0.9028 L, T, 0.6039 1.5481 45.75

S, CS 0.1531 R, -1.0857 L; T, 0.4305 1.7847 26.08

S, 0.0591 R, 2.2744 L, T 0.1046 1.5038 66.99

' S, 0.0027 R 2.6585 L T, 0.1112 1.6127 58.58

Lens Radii Thicknesses N V and Spacings R, +4.713 L, T, 0.160 1.623 58.1

S, 0.948 R, +2289 L, T, 0.345 1.623, 58.1 R, l8.05

S, 0.006 R, +4.793 L, T; 0.130 1.691 54.7

S, 0.545 R, +1 1.46 L, T. 0.321 1.785 26 1 s. 0.003 R +2823 1. 5 T =0.123 1.713 53.9 .R' +1.378

S, 0.462 R +2172 1.. a T, 0.922 1.713 53.9

I s. 0 R 1.5B6 L, 1 T, 0.215 1.564 43.8

('unlinucd Lens Radii Thicknesses N V and spacings 5,, 0.227 R, H.696 1. T 0.379 1.7115 26 l S, 0.050 plane T 0.052 Filter 1.522 595 plane S 0.054 R 8.173 L T 0.184 1.465 65.7

S =CS=0.112 R 1.383 L T 0.513 1.785 26 1 5,, 0.072 R 2.685 L T 0.158 1.465 65.7

S 0.004 R +22.61. L T 0.178 1.465 65.7

wherein all linear dimensions of radii, thicknesses, and spacings are expressed in proportion to the equivalent focal length of the entire lens system, which is considered as unity, and the reference letters and numerals have the respective meaning explained in the specification.

12. A lens system as defined in claim 1, wherein the 25 characteristics of the lens elements and their spatial relationship to each other are substantially in the proportions indicated by the data in the following table:

foregoing wherem all lmear d1mens1ons of rad11, th1cknesses, and spacmgs are expressed 1n proport10n to the equ1valent Lens Radii Thicknesscs N V and Spacings s 0.788 R +3.316 L, T 0.122 1.691 54.7

5 0.706 R +12.37 L, Ta 0.311 1.785 26.1

s, 0.061 R. +2505 L. T. 1 0.093 1.713 53.9

s. 0.502 R, +3437 L T 0.751 1.713 53.9

. s, 0.056 plane '1'. 0.052 111161 1522 59.5 plane R 0.706 s =cs=0.115

T, 0.469 1.785 26.1 R, -2.469 L111 S11 0 R' +2.469 v 5., 0.0611 R, -3.4117 L., T, 0.142 1.465 65.7

s 0.003 R,, -4.205 L T 06165 1.465 65.7

wherein all linear dimensions of radii. thicknesses, and spacings are expressed in proportion to the equivalent focal length of the entire lens system, which is considered as unity, and the reference letters and numerals have the respective meanings explained in the foregoing specification.

Lens Radii Thicknesses V and Spacings R, +3.472 L. T, 0.205 1.623 58.1

' S, 0.932 R, +4.03) L, T, 0.139 1.691 54.7

S, 0.656 R: +l0.15 L; T, 0.342 1.785 26.1

S, 0.008 R. +2.859 L, T. =0.168 1.713 53.9

S. 0.457 R, +2.423 L, T, 0.915 1.713 53.9

S, 0 R, 1.324 L, T, 0.223 1.564 43.8

S, 0.004 R, +1.740 L-, T, 0.048 1.788 47.4

S, 0.223 R, +1.715 l... T, 0.368 1.785' 26.1

Sn ".1149 plane T. 0.053 filler 1.5 22 59.5 plane S. 0.047 R, 58.72 L, T 0.177 1.465 65.7

S CS 0.106 R 1.551 L '1' 0.510 1.785 26.1-

I S 0.079 R 2.604 L T 0.165 1.465 65.7

8,, 0.004 R +13.34 L T 0.182 1.465 65.7 

1. A wide angle lens system with a relatively long back focus on the image side and a relatively large angle of view, comprising a rear member behind an aperture space and a front member in front of said aperture space, said rear member comprising at least three lens elements each with air on both sides, the forward element adjacent said aperture space being a negative element followed in a rearward direction by two positive elements, said front member comprising at least three groups of lens elements, each group having a negative component at the front of the group and a positive component rearwardly of such negative component, the negative component and positive component of each group enclosing between them a diverging-acting air space constituting a negative air lens, each of said air lenses having a more strongly diverging glass-air surface which is concave toward an image at the rear of the lens system, the successive groups in order from the aperture space forwardly being respectively designed Gr. (a) and Gr. (b) and Gr. (c), the lens elements being so constructed that:
 1. The paraxial focal length (fa) of the rearmost group Gr. (a) of the front member is between the limits of 1.134 times and 2.055 times the equivalent focal length (F) of the entire lens system.
 2. The absolute value of the paraxial focal length (fb) of the group Gr. (b) is between the limits of 8.148F and 2.433 F.
 2. The absolute value of the paraxial focal length (fb) of the group Gr. (b) is between the limits of 8.148F and 2.433 F.
 2. A lens system as defined in claim 1, having in its front member a fourth group Gr. (d) arranged forwardly of Gr. (c), the paraxial focal length (fd) of this group Gr. (d) is, in its negative value, within the limits of 5.826 F and 7.724 F.
 3. A lens system as defined in claim 2, wherein said fourth group Gr. (d) consists of only a single lens element which element is negative and which acts as the equivalent of a group having both a negative and a positive element, the air lens of said fourth group Gr. (d) being formed between the rear surface of said single element and the front surface of the negative component at the front of the next succeeding group Gr. (c) behind said fourth group Gr. (d).
 3. The numerical value of the paraxial focal length (fc,b) of the combination of the two groups Gr. (c) and Gr. (b) has an absolute value between the limits of 2.40 F and 5.373 F.
 3. The numerical value of the paraxial focal length (fc,b) of the combination of the two groups Gr. (c) and Gr. (b) has an absolute value between the limits of 2.40 F and 5.373 F.
 4. A lens system as defined in claim 2, wherein the air lens refractive power ( phi ) of the air lens ( delta ) of the fourth group Gr. (d) is, in its negative value, within the limits of 0.145 Phi and 0.336 in which Phi is the equivalent refractive power of the entire lens system, being 1/F.
 5. A lens system as defined in claim 4, characterized by the fact that said fourth group Gr. (d) does not include any positive lens element, and that the air lens ( delta ) of the fourth group is formed between a meniscus shaped negative lens of the fourth group and the front lens of the third group Gr. (c).
 6. A lens system as defined in claim 1, wherein the air lens refractive power ( phi ) as the sum of the surface refractive powers of the two radii of curvature enclosing the air lens gamma in the group Gr. (c) is so dimensioned that the negative value of gamma is within the limits of 0.291 Phi and 0.390 in which Phi is the equivalent refractive power of the entire lens system, being 1/F.
 7. A lens sytem as defined in claim 1, characterized by he fact that a lens component in the vicinity of said aperture space is divided into two lens elements with a finite air space between them, and a filter is interposed in said air space.
 8. A lens system as defined in claim 7, wherein said divided component is the component next in front of said aperture space, being the rearmost component of the rearmost group Gr. (a) of the front member (Vgl of the lens system.
 9. A lens system as defined in claim 1, wherein the characteristics of the lens elements and their spatial relationship to each other are substantially in the proportions indicated by the data in the following table:
 10. A lens system as defined in claim 1, wherein the characteristics of the lens elements and their spatial relationship to each other are substantially in the proportions indicated by the data in the following table:
 11. A lens system as defined in claim 1, wherein the characteristics of the lens elements and their spatial relationship to each other are substantially in the proportions indicated by the data in the following table:
 12. A lens system as defined in claim 1, wherein the characteristics of the lens elements and their spatial relationship to each other are substantially in the proportions indicated by the data in the following table:
 13. A lens system as defined in claim 1, wherein the characteristics of the lens elements and their spatial relationship to each other are substantially in the proportions indicated by the data in the following table: 